IDS Forum

Re: Informix 12 Unicode

Posted By: Fernando Nunes
Date: Wednesday, 22 October 2014, at 7:50 a.m.

In Response To: Re: Informix 12 Unicode (Martin Fuerderer)

That is good. But I think the issue the OP is facing (which I think is very
common), is that it's impossible to know how many characters we're able to
store in a column, because we don't guarantee that...
This seems to be a fundamental design structure... Big O for example allows
you to specify:

CREATE TABLE ... ( col1 VARCHAR2(30 CHAR))

This means you'll always be able to fit 30 characters, no matter how many
bytes it takes. There is a disclaimer stating that if you do something like:

CREATE TABLE... ( col1 VARCHAR2(4000)) -- 4000 is the "hard limit" of
VARCHAR2.

Then it's not guaranteed that you'll be able to store 4000 characters... it
will accept up to the maximum bytes (4000) allowed in the datatype).
I think big O is also able to "extend" CHAR fields... but I'm not really
sure.

It could be easier to implement this (just for VARCHAR) in Informix....
Since by design (AFAIK) varchar(N) doesn't impose any physical limit on the
row.
My concern is that because our VARCHAR() limit is relatively low (256) that
this could easily lead to columns exceeding the byte limit....

And this, in turn, leads to the other possible discussion about this: We
don't raise an error when the user tries to exceed the limit.....
(INSERTing a VARCHAR(200) in a VARCHAR(100) column). We just truncate the
data without warning.
From my point of view (and I recently had customers complaining about that)
this is an undesirable behavior (not a bug as it works as design).
There is an RFE for this.... and because we raise an error on ANSI
databases, I'd expect this change to classify as "very possible", but
without seeing the code I can only imagine.

So.... in short I would:
1- Open an RFE to request the specification of CHAR (as opposed to bytes)
for variable length fields (VARCHAR/LVARCHAR)
2- Vote for the existing RFE to create a configuration option ($ONCONFIG,
SET ENVIRONMENT....) to force the raise of an error if we insert a
character string that does not fit the column. That RFE is:
http://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=33830

There seems to be a duplicate (not yet classified as such):

http://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=53804

Hopefully if the first one gets implemented, R&D will consider my
comments.... I think the original request for a "warning" is not enough. An
error is necessary in order to be useful for existing applications.

Regarding the first RFE, AFIK it's not inserted yet... but a carefull
search would be needed. Implementing it for VARCHAR seems much easier than
for CHAR...
Regards.

On Wed, Oct 22, 2014 at 11:41 AM, Martin Fuerderer <MARTINFU@de.ibm.com>
wrote:

> Hi,
>
> you may use function ifx_gl_mb_loc_max() in
> an application to determine, how "wide" a
> character can be in the current locale.
>
> Regards, Martin
> --
> Martin Fuerderer
> IBM Informix Development Munich, Germany
> Information Management
>
> Read about the Informix Warehouse Accelerator:
> http://tinyurl.com/the-iwa-blog
>
> IBM Deutschland Research & Development GmbH
> Chairman of the Supervisory Board: Martina Koederitz
> Board of Management: Dirk Wittkopp
> Corporate Seat: Boeblingen, Germany
> Reg.-Gericht: Amtsgericht Stuttgart, HRB 243294
>
> From: "MATTI JAATINEN" <matti.jaatinen@norelco.fi>
> To: ids@iiug.org
> Date: 10/22/2014 10:14
> Subject: Re: Informix 12 Unicode [34012]
> Sent by: ids-bounces@iiug.org
>
> Hi,
>
> http://www.iiug.org/forums/ids/index.cgi/read/34002
>
> Char_length return length of the characters in data not the length of
> column. Example you have
>
> column sar1 char(5) and there is row which data is '4ä4'.
> Char_length(sar1)
> return 3 pecause there is 3 characters in that row. Length(sar1) return 4
> pecause there is 4 bytes in that row.
>
> The problem is how to determine how many characted can be put into the
> column
> sar1. Informix reports column size as byte-size so i appears that there is
>
> enought space for 5 characters, but when we use myltibyte characters eq.
> '&#39740;' there can be put only 1-characted into column sar1.
>
>
>
> *******************************************************************************
>
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

--001a113f7d5e6069310506018ca1

Messages In This Thread

• Informix 12 Unicode
  MATTI JAATINEN -- Tuesday, 21 October 2014, at 5:34 a.m.
  • Re: Informix 12 Unicode
    MATTI JAATINEN -- Tuesday, 21 October 2014, at 9:16 a.m.
    • Re: Informix 12 Unicode
      MATTI JAATINEN -- Tuesday, 21 October 2014, at 9:46 a.m.
      • Re: Informix 12 Unicode
        Fernando Nunes -- Tuesday, 21 October 2014, at 11:15 a.m.
        • Re: Informix 12 Unicode
          Fernando Nunes -- Tuesday, 21 October 2014, at 11:58 a.m.
          • Re: Informix 12 Unicode
            MATTI JAATINEN -- Wednesday, 22 October 2014, at 1:50 a.m.
            • Re: Informix 12 Unicode
              Martin Fuerderer -- Wednesday, 22 October 2014, at 3:56 a.m.
              • Re: Informix 12 Unicode
                MATTI JAATINEN -- Wednesday, 22 October 2014, at 4:14 a.m.
                • Re: Informix 12 Unicode
                  Martin Fuerderer -- Wednesday, 22 October 2014, at 6:41 a.m.
                  • Re: Informix 12 Unicode
                    Fernando Nunes -- Wednesday, 22 October 2014, at 7:50 a.m.
                    • Re: Informix 12 Unicode
                      Fernando Nunes -- Wednesday, 22 October 2014, at 9:33 a.m.
                  • Re: Informix 12 Unicode
                    Fernando Nunes -- Wednesday, 22 October 2014, at 9:24 a.m.
                    • Re: Informix 12 Unicode
                      MATTI JAATINEN -- Thursday, 23 October 2014, at 1:11 a.m.
            • Re: Informix 12 Unicode
              Fernando Nunes -- Wednesday, 22 October 2014, at 5:30 a.m.
  • Re: Informix 12 Unicode
    Fernando Nunes -- Tuesday, 21 October 2014, at 9:58 a.m.
    • Re: Informix 12 Unicode
      MATTI JAATINEN -- Tuesday, 21 October 2014, at 10:13 a.m.
      • Re: Informix 12 Unicode
        Fernando Nunes -- Tuesday, 21 October 2014, at 11:07 a.m.

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